1. Field of the Invention
The present invention relates to an engine temperature display device for a watercraft propulsion unit and a watercraft including an engine state display device for displaying an engine temperature, which is one of the display factors of an engine state, on a display device on a watercraft.
2. Description of the Related Art
One of the display factors of an engine state of an outboard motor is the engine temperature (i.e., an engine coolant temperature). Conventionally, a signal from a sensor for detecting an engine coolant temperature is input to an engine control unit. Data about the engine coolant temperature is sent from the engine control unit to a display device on a watercraft by a LAN (Local Area Network), and displayed thereon.
JP-A-2005-164743 discloses an engine state display device for a watercraft propulsion unit including an engine state display device in which a state data value obtained by detecting each state of an engine of an outboard motor is sent by the LAN, wherein the state data value is input to a Central processing Unit (CPU) via a transmission module, the state data value is computed based on display information stored in a nonvolatile memory in the CPU and converted into display data among a plurality of temperature levels, and the display data is displayed on a display device via a display driver.
In the engine state display device for the watercraft propulsion unit, a plurality of threshold temperatures on the engine coolant temperature is previously stored as the display information in the nonvolatile memory. When a detection signal of a temperature sensor for detecting the engine coolant temperature, which is sent by the LAN, is input, the CPU calculates an engine coolant temperature, compares the engine coolant temperature with a plurality of threshold temperatures, and thereby converts the engine coolant temperature into the display data for displaying the engine coolant temperature in five levels.
However, in the engine state display device for the watercraft propulsion unit in JP-A-2005-164743, the plurality of threshold temperatures on engine coolant temperature stored in the nonvolatile memory is commonly used among many outboard motor models. On the other hand, since the engine coolant temperature level sent from the engine control unit of the outboard motor may be different model, there is a case that a state data value is computed based on the display information (e.g., the plurality of threshold temperatures on the engine coolant temperature) of a different model and the display data is output. In such a case, an engine coolant temperature displayed on the display device is not an advisable temperature level. For example, if the display information for a model with high engine coolant temperatures is used in a model with low engine coolant temperatures, the display device of the engine state display device for the watercraft propulsion unit may display a high temperature level based on the model with high engine coolant temperatures, and as a result a user may be concerned that the engine coolant temperature is too high for the model with low engine coolant temperatures.
Therefore, in models in which engine coolant temperatures are different, for example, a model with high engine coolant temperatures requires a new temperature sensor in an appropriate position such that an engine coolant temperature can be appropriately detected, and thereby a system for displaying the appropriate temperature levels is provided.
However, such a system requires more parts and assembly steps, and also costs more.